1. Field of the Invention
The present invention relates to a reconfigurable optical amplifier and applications thereof.
2. Description of Related Art
Optical communication techniques have been broadly applied to ultra-wideband networks, wherein reversible three-port or four-port optical circulators are usually used as unidirectional 1×2 and 2×2 optical switches. In addition, optical amplifiers composed of optical circulators with fixed transmission directions and optical gain devices are usually disposed on optical transmission paths for amplifying optical signals and providing network monitoring signal return paths. A conventional optical amplifier has a unidirectional design, and therefore is limited in network applications.
FIG. 1 is a schematic diagram of a conventional optical communication network. Referring to FIG. 1, in the conventional optical communication network, a two-way transmission is established between two communication nodes 80 and 90. The communication node 80 has a receiver Rx1 and a transmitter Tx1, and the communication node 90 has a receiver Rx2 and a transmitter Tx2 respectively connected to the transmitter Tx1 and the receiver Rx1. Taking that the communication node 80 transmits an optical signal to the communication node 90 as an example, the communication path is connected to the receiver Rx2 of the communication node 90 through an optical switch 100, a unidirectional optical amplifier (OA) 102, an optical fiber path 104, a unidirectional optical amplifier 106, and an optical switch 108.
However, the optical fiber path 104 may be broken due to some external factors. Thus, a protection path 120 has to be disposed, and the optical signal can be transmitted through the protection path 120 through the switching of the optical switches 100 and 108. The protection path 120 is the same as a normal path but only served as a backup path.
Similarly, when the communication node 90 transmits an optical signal to the receiver Rx1 of the communication node 80, the communication path is connected to the receiver Rx1 of the communication node 80 through an optical switch 110, a unidirectional optical amplifier 112, an optical fiber path 114, a unidirectional optical amplifier 116, and an optical switch 118. The backup protection path 122 has the same function as the protection path 120 but a reverse transmission direction. Because optical amplifiers are usually used in unidirectional transmission only, two protection paths 120 and 122 have to be disposed. As a result, the cost of the conventional optical communication network is very high.
Even though many different designs have been provided, a more satisfactory optical communication technique is still desired.